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- Mossmark, Fredrik, 1975, et al.
(författare)
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Aggressive groundwater chemistry caused by underground constructions
- 2008
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Ingår i: Proceedings of the 33rd International Geological Congress, Oslo, Norway, August 2008.
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Konferensbidrag (refereegranskat)abstract
- When considering the degradation process and lifetime of the support system and equipment in underground facilities, the selection of materials is (normally) based on established criteria for the chemical composition of the groundwater. This is important for decisions regarding the steel quality and protection of reinforcement bolts, as well as the material used for the waterproofing system and lining. The criteria are imposed through groundwater sampling and analysis of groundwater prior to the construction of an underground facility. However, studies of the impact on groundwater chemistry from the construction of underground structures and experiments with groundwater extraction indicate that the groundwater chemistry is likely to change over time. Underground facilities are known to cause hydrological changes, especially during the construction phase. However, extensive monitoring programmes of groundwater chemistry are unusual. To further investigate possible changes of water chemistry due to hydrological changes, an experiment with groundwater extraction has been carried out. The experiment was conducted through the constant extraction of groundwater for a period of five years (between the years 2000 and 2005) from within a small watershed (28000 m2) at Lake Gårdsjön, located 50 km north of Gothenburg in Sweden. The area was also monitored during a few years before the extraction started and during the recovery phase. The area of the experiment is characterized by Precambrian crystalline bedrock covered by a thin overburden of glacial till and organic soils. The extraction caused the runoff from the watershed to decrease by nearly 50 % and the groundwater level to fluctuate more than at a nearby reference area. The hydrological impact of the experiment, with increased groundwater recharge, lead to changes and increased seasonal variations in the chemical composition of the groundwater in the bedrock. The hydrochemical variations were caused by seasonal variations in both the amount of water available for groundwater recharge and the chemical composition of the recharging water. Compared to the reference area, the seasonal variations were observed to increase for all the parameters included in the criteria used by the Swedish authorities for selection of construction materials (pH, hardness (Ca), alkalinity, salinity (EC)). An established method to assess the impact of the water composition on the corrosion of steel materials is the use of Langeliers index. The experiment with groundwater extraction caused a larger fluctuation of Langeliers index in the test area compared to the reference area. The results from the experiment confirm the observations from previous tunnelling projects, and show that the methods commonly used to assess the expected future aggressivity of the groundwater in the planning for underground facilities should be reviewed.
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- Mossmark, Fredrik, 1975, et al.
(författare)
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Effects of groundwater extraction from crystalline hard rock on water chemistry in an acid forested catchment at Gardsjon, Sweden
- 2007
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 22:6, s. 1157-1166
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric deposition of S in Sweden has decreased by some 80% over the last 15 a, resulting in a general reduction of SO4 concentrations in ground and surface water. This project, however, shows that artificial hydrological alteration in an acid wetland can reverse this trend and increase acidity and SO4 concentrations. The experiment involved the monitoring of two catchments in relatively virgin conditions. In one of the catchments, an experiment with intensive groundwater extraction from the bedrock was carried out. During the experiment, the runoff from the catchment decreased by 50%. Furthermore, the extraction of groundwater resulted in increased seasonal aeration of the centrally located wetland, leading to oxidation of reduced S bound to the soil layers of the wetland. The S changed to solute SO4, with a subsequent SO4 surge. Thus, the experiment resulted in an induced acidification of the wetland and runoff waters. The extraction of groundwater significantly increased the recharge of water from the overburden, glacial till and organic soils to groundwater in the bedrock, which in turn reduced the retention time in the bedrock aquifer. These changes resulted in the chemical signature of the groundwater in the bedrock becoming similar to those of the wetland., The findings revealed deterioration in the water quality in the bedrock due to increased concentrations of dissolved organic C and SO4, as well as a decrease in pH. (c) 2007 Elsevier Ltd. All rights reserved.
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- Mossmark, Fredrik, 1975, et al.
(författare)
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Recovery from groundwater extraction in a small catchment area with crystalline bedrock and thin soil cover in Sweden
- 2008
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 404:2-3, s. 253-261
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Tidskriftsartikel (refereegranskat)abstract
- An experiment has been in progress since 1997 in a small catchment area (28,000 m2) with crystalline bedrock and thin soil cover to study the conceivable impact on groundwater conditions of tunneling and the use of groundwater. The impact on hydrology and hydrochemistry from intensive extraction of groundwater at a depth of 50 m in the bedrock has been studied at Lake Gårdsjön in Sweden. The catchment area was first monitored under pristine conditions, followed by four and a half years of extraction and then a recovery phase. The geological conditions result in a low buffer capacity and high sensitivity to acidification. During the period of extraction, the surface runoff decreased by approximately 50% compared to a nearby reference area. The groundwater extraction caused increased fluctuation in groundwater levels in a wetland, which in turn caused oxidation of reduced sulfur to sulfate. The sulfate concentrations increased almost 100-fold in some instances, causing a lowering of the pH by one unit in shallow groundwater. Since extraction of the groundwater was discontinued, the pH has gradually risen and the sulfate concentrations have decreased. However, the concentration of sulfate in groundwater in the wetland has remained stable at approximately double the pre-experiment levels. Magnesium concentrations were lower after the experiment, caused by exhaustion of the magnesium pool in the wetland through acidification. The extraction of water from the bedrock shortened the retention times and increased the recharge of groundwater in the bedrock. After extraction was terminated, the groundwater levels in the boreholes recovered within a month to levels similar to those before extraction. The hydrochemistry of the bedrock groundwater, which was strongly affected by the hydrochemistry of shallow groundwater during the experiment, has also gradually begun to regain its pre-extraction signature. However, the surface runoff has remained low during the first 2 years of recovery, at about 60% of the volume compared to the unaffected catchment area. This could be explained by delayed recovery in resaturation of the shallow rock that was unsaturated during the experiment.
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- Pant, Neha, et al.
(författare)
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Lactobacilli expressing variable domain of llama heavy-chain antibody fragments (lactobodies) confer protection against rotavirus-induced diarrhea
- 2006
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Ingår i: Journal of Infectious Diseases. - 0022-1899 .- 1537-6613. ; 194:11, s. 1580-1588
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Tidskriftsartikel (refereegranskat)abstract
- Background. Rotavirus-induced diarrhea poses a worldwide medical problem in causing substantial morbidity and mortality among children in developing countries. We therefore developed a system for passive immunotherapy in which recombinant lactobacilli constitutively express neutralizing variable domain of llama heavy-chain (VHH) antibody fragments against rotavirus. Methods. VHH were expressed in Lactobacillus paracasei, in both secreted and cell surface-anchored forms. Electron microscopy was used to investigate the binding efficacy of VHH-expressing lactobacilli. To investigate the in vivo function of VHH-expressing lactobacilli, a mouse pup model of rotavirus infection was used. Results. Efficient binding of the VHH antibody fragments to rotavirus was shown by enzyme-linked immunosorbent assay and scanning electron microscopy. VHH fragments expressed by lactobacilli conferred a significant reduction in infection in cell cultures. When administered orally, lactobacilli-producing surface-expressed VHH markedly shortened disease duration, severity, and viral load in a mouse model of rotavirus-induced diarrhea when administered both fresh and in a freeze-dried form. Conclusions. Transformed lactobacilli may form the basis of a novel form of prophylactic treatment against rotavirus infections and other diarrheal diseases. © 2006 by the Infectious Diseases Society of America. All rights reserved.
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